Earth Fault Detection Research Articles

Kernel‐PCA‐based single‐phase earth fault detection model using multilayer perceptron in deep learning

AbstractThe rapid and accurate identification of single‐phase earth fault is of prime concern for many scholars from industry and academia, because its fault characteristics are extremely weak while the related potential hazard is extremely severe. In this context, this paper borrows from Deep Learning and in turn innovatively puts forward a multilayer perceptron (MLP)‐based single‐phase earth fault detection model augmented with kernel principal component analysis (KPCA). First, KPCA is applied to building fault feature extraction engineering via the transformation of fault features from low‐dimensional linear indivisible space to high‐dimensional one. Second, a MLP‐based model is used for basic model reference where many optimization strategies together with dropout technique are introduced and custom‐designed in tuning this model to achieve the best detection accuracy and convergence characteristic. Numerical studies demonstrate the superiority of the proposed KPCA‐MLP‐based single‐phase earth fault detection model.

Simultaneous series and shunt earth fault detection and classification using the Clarke transform for power transmission systems under different fault scenarios

For high-voltage (symmetric and non-symmetric) transmission networks, detecting simultaneous faults utilizing a single-end-based scheme is complex. In this regard, this paper suggests novel schemes for detecting simultaneous faults. The proposed schemes comprise two different stages: fault detection and identification and fault classification. The first proposed scheme needs communication links among both ends (sending and receiving) to detect and identify the fault. This communication link between both ends is used to send and receive three-phase current magnitudes for sending and receiving ends in the proposed fault detection (PFD) unit at both ends. The second proposed scheme starts with proposed fault classification (PFC) units at both ends. The proposed classification technique applies the Clarke transform on local current signals to classify the open conductor and simultaneous faults. The sign of all current Clarke components is the primary key for distinguishing between all types of simultaneous low-impedance and high-impedance faults. The fault detection time of the proposed schemes reaches 20 ms. The alternative transient program (ATP) package simulates a 500 kV–150-mile transmission line. The simulation studies are carried out to assess the suggested fault detection and identification and fault classification scheme performance under various OCFs and simultaneous earth faults in un-transposed and transposed TLs. The behavior of the proposed schemes is tested and validated by considering different fault scenarios with varying locations of fault, inception angles, fault resistance, and noise. A comparative study of the proposed schemes and other techniques is presented. Furthermore, the proposed schemes are extended to another transmission line, such as the 400 kV–144 km line. The obtained results demonstrated the effectiveness and reliability of the proposed scheme in correctly detecting simultaneous faults, low-impedance faults, and high-impedance faults.

Improving the Efficiency of Earth Fault Detection by Fault Current Passage Indicators in Medium-Voltage Compensated Overhead Networks

The article presents a method for detecting earth faults in a compensated medium-voltage network, which can be used especially in fault current passage indicators, but also in standard protection devices. The method is based on the adaptation process of the zero-sequence current protection setting, with the adaptation factor depending on the current value of the zero-sequence voltage. In this article, a comparative analysis of the classical and adaptive zero-sequence current criterion is conducted, taking into account the errors of the measuring system. The results of simulations performed in the PSCad environment are also presented. For a representative set of example short circuits, it was shown that the effectiveness of the presented criterion can be more than 50% higher than that of the standard criteria, taking into account the range of detected transition resistances. A comparison of the proposed method with admittance criteria was also drawn, and it was shown that it is suitable for the detection of high-resistance earth faults.

Stator earth fault detection & evaluation of delaminated stator bar ground wall-insulation of generator G-4 of HPP Chhukha – A case study

Protective devices are employed to monitor and isolate the faulty equipment whenever faults occur in the power system. In the generator protection system, a conventional stator earth fault protection, which is based on residual over voltage (aka neutral voltage displacement) principle, is observed to be inadequate. The paper thus, discusses on how helpful a modern approach of 100% stator earth fault protection scheme is, and proven effective in generator G- 4 of Chhukha Hydropower Plant (CHP). Also, to assess the health of stator windings, insulation resistance (IR) measurement is the foremost test that needs to be performed to qualify for go- ahead with other insulation tests. HV DC ramp and tan ẟ tests are not uncommon as the tests have been proven useful in evaluating the condition of the groundwall insulation of stator coils. Therefore, this paper also illustrates on investigation and analysis of the test results obtained for a bar, suspected to have groundwall insulation breakdown, due to a number of factors. The test results obtained are compared with that of the other test specimens.

Distance Protection of Transmission Lines in Presence of Inverter-Based Resources: A New Earth Fault Detection Scheme During Asymmetrical Power Swings

Although it is commonly assumed that power swing is symmetrical and will have identical effects on all three-phase voltages and currents, there is another type of power swing, which is asymmetrical and mainly occurs during single-pole tripping (SPT), the impact of which on power systems integrated with the inverter-based resources (IBRs) has not been investigated so far. Since the likelihood of the occurrence of asymmetrical power swing is increasing in today's heavily loaded transmission lines, this article investigates the impact of IBR integration on the performance of distance protection during single-pole tripping. Furthermore, a new scheme is proposed to detect earth faults that occur during asymmetrical power swings to enhance the performance of power swing blocking functions. To do so, the superimposed component of the zero-sequence current during SPT is extracted. Then, the moving average window is used to calculate the average of both zero-sequence current and its superimposed component. Furthermore, to enhance the security of the proposed scheme, a new technique based on the phase angle shift between the three-phase currents is devised to detect the asymmetrical power swing conditions. This article shows that as the penetration level of IBRs increases, the standard reclosing dead-time needs to be revisited otherwise it can create an unstable power swing condition, even during SPT. Moreover, this article shows that the proposed earth fault detection scheme can efficiently detect all single-line-to-ground faults occurring during SPT.

Monitoring, Detection and Locating of Transient Earth Fault Using Zero-Sequence Current and Cable Screen Earthing Current in Medium Voltage Cable and Mixed Feeders

This paper presents the final development of an expert system utilizing a measurement of cable screen earthing transient current. The developed system allows for identification and location of earth fault in underground cable and mixed lines (underground cable and overhead line) and monitoring of an earthing system and cable screen connections. The unique feature of the developed earth fault locating system is the possibility of identification of line type and branch of the MV underground cable or mixed feeder under earth fault conditions. As a result, the time to remove failure can be greatly reduced and the number of earth fault indicators installed in the distribution network can also be reduced. Unfortunately, in order to operate properly, the previously developed system requires a fundamental—50 Hz component of the measured zero-sequence cable core current and cable screen earthing current; therefore, short transient earth faults without steady-state earth fault currents cannot be localized and categorized even though the transient earth faults have a negative impact on the power system. According to measurements performed by the authors, transient earth faults are relatively frequent, which causes stress to insulation. The number of transient earth faults may be reduced by ensuring proper maintenance of the distribution system. Unfortunately, because of the very large area of the distribution feeder, often in the range of tens of kilometers or even around a hundred kilometers, and many potential causes of earth faults, it is very difficult to localize the transient earth fault and determine the cause of the earth fault. Herein, we present the possible causes of transient earth faults and methods developed for the analysis of transient earth faults. Moreover, the novel algorithm for transient earth fault detection and location is proposed. The proposed algorithm has a self-learning capability and can identify branches of the distribution feeder under transient earth fault conditions. The effectiveness of the proposed algorithm is confirmed thanks to the performed network experiment.

Earth fault detection in distributed power systems on the basis of artificial neural networks approach

Nowadays, the advancement of microgrids promises numerous economic and environmental advantages of renewable energies to nations and societies. The presence of decentralized energy units, however, makes serious technical challenges; for instance, criteria and procedure of fault recognition and diagnosis in this condition is entirely changing. This article, therefore, proposed a novel accurate and fast technique based on Artificial Neural Networks (ANN) for earth fault detection. A sample distributed power system considered for the proposed technique and different earth faults applied to this system consist of one phase, two phases and three phases faults. Also, any alteration of current and voltage signals of all phases is investigated at the fault occurrence moment. Analysis of simulation results demonstrates how the proposed technique could make faster responses and improve the reliability of the distributed power system by more accurate fault recognition in comparison with the other traditional methods such as the Wavelet Transformation technique. The proposed technique is likely to enhance the growth of renewable energy sources usage by decreasing operational risk factors and fault recognition delays.

Alternative method of determining zero-sequence voltage for fault current passage indicators in overhead medium voltage networks

Zero-sequence voltage is one of the main quantities that serve as a criterion for detecting earth faults in medium voltage networks. This paper presents a novel but simple method of determining zero-sequence voltage for smart grid protection devices, especially for use in fault current passage indicators. The presented method can also be used to measure zero-sequence voltage in any point of the network, where such values are required and application of other classical measurement methods is not possible. The method is based on continuous measurement of only one phase-to-earth voltage performed by an overhead voltage sensor. Both laboratory and field tests of the proposed method were carried out and their results indicate that the maximum expected relative error in determining the zero-sequence voltage is δU0=10,15%. Taking into account the simplification applied in the method, the obtained measurement results are sufficient to be used in the earth fault detection criteria in fault current passage indicators. The use of the proposed method allows to reduce the installation cost of this type of devices, while maintaining their high efficiency.

Earth-fault detection and localization in isolated industrial MV network – comparison of directional overcurrent protection and signal injection method

Neutral earthing directly affects systems' behaviour regarding the maximum level of earth-fault current and overvoltages. Isolated neutral is used where continuity of power supply is essential, which is often the case in industrial power utilities. Although the system can remain in service during a single-phase earth-fault, locating the fault should be done as quickly as possible, without disrupting the operation of the loads. Directional earth-fault protection (67N) can be used to indicate the faulty feeder. An alternative method is low-frequency (LF) current injection combined with sensors for detecting the injected signal, which is a known technique used in LV systems. In this paper, the application of 67N protection and the LF current injection method are tested on the same MV system with inaccessible neutral point. Inductive voltage transformers (IVTs) are used for signal injection. Both methods are discussed, and their limitations are compared based on simulation results obtained using the model of an isolated MV industrial plant. The model includes relay protection devices and IVTs for signal injection.

Utilization of Cable Screen Earthing Current for Detection and Location of Earth Faults in Medium Voltage Networks

The paper presents issues related with detection and location of earth faults in medium voltage (MV) networks. Attention is paid on cable and cable-overhead lines. The criterion value – cable screen earthing current is presented. Afterwards, the method of utilization of the cable screen earthing current for detection and location of earth faults is described. The next part of the paper presents the results of simulation research for different variants of earth faults in cable and cable-overhead lines. The presented relations are the basis of the developed algorithm of detection and localization of earth faults. The presented considerations were confirmed by an experiment performed in the MV network.

Adaptive Zero-Sequence Overcurrent Criterion for Earth Fault Detection for Fault Current Passage Indicators in Resistor Grounded Medium Voltage Networks

Earth faults are the most common disturbances in medium voltage networks. They cause threats to equipment and people, and reduce the quality and reliability of electricity supply. Detection and localization of earth faults is a key challenge to network operators, therefore it is important to constantly develop criteria that allow for an unequivocal assessment of the current network state. This article focuses analysis of effectiveness of classic zero-sequence overcurrent criterion and on modification of the zero-sequence overcurrent criterion applied in fault current passage indicators, which are the devices used to effectively detect and locate earth faults. Two new adaptation criteria for networks with resistor grounded neutral point have been proposed, which enable significant improvement of the effectiveness of earth faults detection, in particular high impedance ones. The effectiveness of the criteria was verified computationally and in simulations. In certain situations, the proposed solutions may be over 40% more effective than the classic criterion. The value of detected transition resistance $R_{F} $ also increases significantly. All the above-mentioned advantages make their potential use in practice very beneficial.

New approach to intermittent earth fault detection with admittance criteria

Admittance based tripping criteria afford reliable earth fault protection of MV distribution feeders. Although highly effective for persistent earth fault detection, they often fail in the case of intermittent arcing faults when employed in the conventional protection schemes. In this paper the new approach to persistent and intermittent earth faults detection is proposed. The method is based on calculation of the cumulative intermittent arcing fault duration time. The validation based on data from numerical modeling of earth faults in EMTP as well as data recorded in real MV networks confirms the effectiveness of the approach.

Detection and Location of Earth Fault in MV Feeders Using Screen Earthing Current Measurements

The paper analyzes the utilization of cable screen currents for earth fault identification and location. Attention is paid on cable and mixed feeders—cable and overhead lines. The principle of operation is based on utilization of 3 criterion values: Ratio of cable screen earthing current and zero sequence cable core current—RF110/15, phase shift between cable screen earthing current and zero sequence cable core current—α and cable screen admittance defined as a ratio of cable screen earthing current and zero sequence voltage—Y0cs. Earth fault location is possible thanks to discovered relation between RF110/15 and α, whereas Y0cs allows for reliable detection of earth faults. Detection and identification are very important because it allows to increase the reliability of supply—reduce downtime and number of consumers affected by the fault. The article presents a phase to ground fault current flow for different power system configurations. At the end solution, which improves location capabilities is proposed. The solution is analyzed in PSCAD software and verified by network experiment.

Optimized bandpass admittance criteria for earth fault protection of MV distribution networks

This paper is concerned with the new method of earth fault detecting in MV distribution networks. The goal of investigations was to enhance protection sensitivity to low resistance faults resulting in small increase of voltage and residual currents in protected feeders. The earth fault detection criteria for three earthing methods and details of the criteria optimization algorithm are presented. The multi-option protection criteria optimization was based on relaying signals obtained from MV distribution network modelling in EMTP. The reliability of the protection algorithm for sustained and intermittent arcing earth faults is discussed.

DESIGNING OVERVOLTAGE AND UNDERVOLTAGE TRIPPING CIRCUIT FOR DISTRIBUTED SYSTEM LOAD WITH GSM ALERT USING MICROCONTROLLER

The main aims of this project to alert the relay when some difference in supply power for shield electrical home equipment and industrial instrument under over-voltage and under-voltage. The chances of damaged electronic devices are more because the equipment is much conscious in different power supply. In this scenario, it needs an extra shield system to shield the instrument by a different power. With the voltage comparator integrated circuits decide the trip of relay system get function as the voltage differs higher than or down the set worth. The major profit by that it also shields the 3-phase device from 1-phase and variation of power in ac power waveform. In the coming days it also possible earth fault detection and protection.

The influence of the network asymmetry on the settings and sensitivity of an earth fault protection using higher harmonics

Detection of high resistance earth faults in medium voltage networks is an important problem due to ineffectiveness of traditional earth fault protections. Such short circuits can be detected by the criterion of a reactive power of higher harmonics for zero sequence current and voltage. The main problem is determination of the power setting value in the protection, which depends on the asymmetry of phase-to-earth capacitances and higher harmonics in supply voltages, which are generated by non-linear loads. The intensive tests of the asymmetry of the zero sequence currents and voltages for harmonics and their reactive power have been carried out in 15 kV compensated network as a function of all relevant parameters, i.e.: maximum capacitance deviation of the network and protected line, percentage content of harmonics in supply voltages, capacitive current of the network and the line. It has been shown that third harmonics of the zero sequence voltage and current are the best suited for practical use, since the asymmetry reactive power of these components is the smallest among the considered harmonics and the protection sensitivity will be the highest.

General earth fault protection for MV networks using wavelet decomposition and Bayesian criterion

For selective detection of earth faults in medium voltage networks, the general protection can be used, which unlike individual protections controls earth currents in all lines supplied from the substation. To detect high-resistance and arc faults, it is possible to use in such protections the details from wavelet decomposition of earth currents and the Bayesian conditional probability criterion. The paper presents a protection model using details of earth currents and the Bayesian criterion. Significant parameters of the model were determined: sampling frequency, wavelet types and decomposition levels, parameters of the probability density function and decision conditions. The effectiveness of the protection in the case of non-stationary high-resistance short-circuits in the network with natural asymmetry and harmonic distortion was also assessed.

New single-ended earthfault distance estimation for the 110-kV- and 20-kV-compensated network

Due to today´s increased demands on grid operation management, new methods for earth fault localization and detection are needed. The fault localization should be performed as quickly as possible and under the condition, that the fault current at the fault location will not be significantly increased.

Sensitive ground fault detection in compensated systems (arc suppression coil). What is influencing the sensitivity?

High-impedance Earth fault detection is always a topic for any kind of neutral point treatment in electrical power line systems. For compensated networks, it is the disseminated opinion that fault detection is too difficult. The authors aim to show it is simpler and much more sensitive compared with other neutral point treatments. Especially for the sensitivity of classical fault detection methods such as wattmetric (cos ϕ), admittance method and transient method, the question is what sensitivity to expect. This study gives a basic overview of the mentioned detection methods, their achievable sensitivity and the requirements for that. Since the fault detection should work with natural signals only, methods with artificial signal injection during the fault are not included. The necessary measurement accuracy for different detection methods will be considered as well. Basic aspects with practical measurements taken during Earth fault tests in a compensated system with overhead lines are compared. The fault impedance was >5 kΩ in the 10 kV system. The earth fault tests have been undertaken with Energijos Skirstymo Operatorius. The device Erdschluss Ortungs Relais-3D (EOR-3D) has been tested regarding the fault detection sensitivity. They will show that classical methods can achieve high fault detection sensitivity.

Application of differential protection to offshore wind farm for earth fault detection with substantially unbalanced charging current

Introduction of renewable resources into the power system has raised significant challenges to the protection system. Conventional ways of working are deemed insufficient and need to be improved. This study will focus on one subject that has often been overlooked – unbalanced charging current. The application of long high voltage submarine cables to connect a large number of wind turbines to offshore substation has resulted in the considerable unbalanced charging current flowing into the system during earth fault. This study will present a real-life application of differential protection to an offshore wind farm network. It will primarily discuss how the existence of unbalanced charging current affects the sensitivity of the differential protection relays. This discussion is further substantiated with actual fault measurements taken from one of Siemens built offshore wind farms. This study will subsequently recommend ways to improve the sensitivity of differential protection based on Siemens’ experience. As more and larger wind farms are built, this study serves a very valuable experience for offshore wind farm protection.